Dr. Malik reported data from an
ongoing phase II study of 148 patients
who had treatment-resistant metastatic
colorectal cancer (CRC) despite prior
treatment with a fluoropyrimidine
(± leucovorin) and either irinotecan
(Camptosar) or oxaliplatin (Eloxatin),
or both. Endpoints included tumor
response (according to RECIST criteria),
time to disease progression, survival,
and safety.

Patients were stratified according
EGFR status. Cohort A included pa-
tients with EGFR staining of 2+ or 3+
in at least 10% of tumor cells. Cohort
B included patients with EGFR staining
of the sum of 1+, 2+, and 3+ in
10% of tumor cells but with the sum
of 2+ and 3+ in < 10% of tumor cells.

Panitumumab was given intravenously
at 2.5 mg/kg once weekly in 8-
week cycles. Treatment continued until
disease progression or unacceptable
toxicity occurred.

Mature Data Confirm
Previous Finding

Panitumumab was active in both
patient cohorts (Table 1). The four
most frequent grade 3 or 4 side effects
were rash, fatigue, vomiting, nausea,
and pruritus. One hundred forty-one
patients (95%) had skin toxicity, including
5% that were grade 3. Dr.
Malik said that one infusion-related
grade 3 adverse event, which did not
require dose modification, was reported,
and there were no human antihuman
antibodies in the 145 patients
tested.

"These mature data confirm previously
reported safety and response
findings and provide encouraging survival
data in patients with metastatic
CRC who have failed multiple lines of
standard chemotherapy," Dr. Malik
said. "Median duration of response
was 18.1 weeks by central review, and
response was seen in patients receiving
up to four lines of prior therapy.
Also, there appeared to be no significant
differences in all efficacy parameters
assessed between cohort A and
cohort B."

Dr. Malik said that panitumumab
is currently being studied in a phase II
trial as third- or fourth-line treatment
in patients with metastatic CRC whose
tumors have low or negative EGFR
expression. The antibody is also in
randomized trials in combination with
bevacizumab (Avastin) and chemotherapy
as first-line therapy.